Friday, September 26, 2014

Mechanical Solutions to 3D Printer Maintenance (The September Project Part VII)

The month isn't over, so we're technically still on track for the September Project timeline with our Bukito 3D printer.   

Those who've read the project notes Part I and Part IV know that we had a stuck screw that derailed some of our plans for earlier in the month, even though we were able to get the printer working with very little trouble.

The screw in the upper position on the extruder shroud (the cover over the hot parts to prevent accidental contact with skin), shown at the point of the arrow above, was seated so tightly that it could not be extracted without stripping the Phillips head. 

Not being able to remove the screw prevented us from being able to install the optional PLA fan shown to the right of the arrow above, but we simply slowed the print speed and proceeded.

Midway through the trial print of the "Hentai Porn Kindle Holder" described in "Part VI", we decided to pause the print to resolve some positioning issues with the object. After that point, we could not get extrusion to happen at all. Either the extruder wasn't heating enough to melt the filament, or the filament was not making it all the way to the extruder nozzle.

Whosa Whatsis (Whosawhatsis) at Deezmaker patiently walked us through or pointed us to several procedures to:
  1. Make sure the extuder nozzle was actually heating,
  2. Address the problem of a clog at the nozzle opening,
  3. "Cold pull" any clog from inside the extruder above the nozzle using ABS, PLA or nylon filament, and
  4. Remove the Bowden tube from the extruder to address clogs in the tube connection to the extruder.
The number 4 procedure would require us to remove the extruder shroud, so we hoped it would not come to that.

Worst Case Scenario

Of course, after eliminating the first three, it came down to number 4. We would have to remove the extruder cover. We had no alternative but to get that stuck screw unstuck.

By this time, from repeated tries at getting it unscrewed, the Phillips-head was a nearly-round divot in the screw head. I went online to research screw-extruder bits, and found a wide range of experiences with them. 

Some tool users said they worked fine, but others cited a real worst case: the extruder-bit broke off in the screw, and then the only option was to have it extracted at a machine shop (lots of $$)! With our luck, we'd be taking the printer to have a broken bit extracted.

Before I gave up and took a chance, I looked at other screw-extraction tools. One, a tool cleverly named VamPLIERS, had a blunt nose with a toothed opening that looked like it was designed to nip into the edges of the screw to assist turning it. While I don't already have a VamPLIERS in my tool-chest, I did have a blunt-nosed pliers with a clipper bite, like broad wire-cutters.

I used these to grip the upper and lower edges of the screw-head, clamped down, and twisted. Voila! Screw moved!

PLA Fan Installed

With the screw removed, the cover off, and the tube disconnected from the extruder, I was able to use a needle-nose pliers to extract an approximately 1-inch long noodle of filament thread from the end of the tube. A quick run-through of test 2 made sure there was nothing still in the nozzle.

While the extruder shroud was still off, we addressed the installation of the optional PLA fan. This was simple, following the well-illustrated step-by-step assembly instructions on the Deezmaker site. Since this was one of the tasks to be accomplished in The September Project, I crossed it off the list.

Still to Come

In the last week or so, we've done many of the intervening tasks from our list. Still left to be addressed are:

  • Modify G-code to tweak a print
  • Create our own 3D model using Trimble SketchUp (a simple one is a cookie cutter, a more complex idea I'll hold back as it may be commercially useful)
  • Develop a presentation incorporating 3D model creation, G-code controls, and production of prints, for delivery to middle-school or high-school STEM groups.

The last is in the first phases of development, following the guidelines from an eBook:
The Invent To Learn Guide to 3D Printing in the Classroom: Recipes for Success. I've made the initial measurements for one of the two 3D models, and we got an excellent book, Mastering 3D Printing by Joan Horvath (the aeronautical engineer who works at Deezmaker) to help with g-code.

So The September Project is really complete, even though we will continue to develop our presentation, and, of course, print objects from the Bukito portable 3D printer.

On to The October Project!